1. Field of the Invention
This invention relates to a bimetallic column for temperature detection operating devices such as a steam trap that automatically obstructs the passage of hot steam but permits the escape of cold condensate in response to the temperature difference between the steam and condensate.
2. Description of the Prior Art
Such a bimetallic column is composed of a plurality of pairs of bimetallic discs superimposed one upon the other. Each pair is spaced apart from an adjacent pair by a spacer and is composed of two opposed bimetallic discs each formed of two different metal or alloy discs bonded together into one integral body. One of the two discs has a high thermal expansion coefficient while the other disc has a low thermal expansion coefficient. In each pair, the metallic discs which are the same in polarity, that is, the same in the thermal expansion coefficient or at least the metallic discs those tend to thermally expand in the same manner are opposed with each other.
The bimetallic column constructed as above described is sensitive to heat and displaced by elongation and hence if it is applied to a steam trap, for example, it is possible to lift a valve stem and hence a valve head from a valve seat. It can be utilized to control the escape of the condensate as above described.
The bimetallic column applied to the steam trap is provided at its center with a hole having a diameter which is slightly larger than an outer diameter of a valve stem extending through the center hole. As a result, if each pair of bimetallic discs are sensitive to heat and deformed, several forces are subjected thereto that tend to incline the valve stem with respect to the bimetallic column and hence urge the valve head against the valve seat, thereby increasing frictional resistance therebetween and restraining the displacement of the bimetallic column and preventing a smooth lift movement of the valve head. In addition, the flow of condensate tends to incline the valve stem to increase sliding resistance to the bimetallic column.